Typically, the capacity of a hard disk drive depends on two parameters, Bit-Per-Inch (BPI) and Track-Per-Inch (TPI). BPI is a function of data rate. The higher the data rate, the higher the BPI. TPI is a function of how closely tracks are written. The closer the tracks are written, the higher the TPI. The product of BPI and TPI equals to the hard drive capacity.
When tracks are placed closer to each other and even overlapping, interference from adjacent tracks becomes significant (e.g., the interference affects the ability to recover the data written to the tracks). For example, the Signal-to-Noise Ratio (SNR) of the track being read can be reduced when the noise due to the adjacent tracks, or Inter-Track-Interference (ITI), is increased. The effects to the data sectors being read include higher Sector-Failure-Rate (SFR) and/or Sync Mark loss, for example.
It would be desirable to reduce the noise introduced by ITI when reading data.